Routing mode and point-of-presence selection service

ABSTRACT

Systems and methods for sloppy routing are provided. A client transmits a DNS query corresponding to a requested resource to a content delivery network (CDN) service provider. In some embodiments, the CDN service provider processes the DNS query to determine whether a threshold content delivery bandwidth has been exceeded by data links at cache servers. In other embodiments, additionally or alternatively, the CDN service provider determines whether a content provider has exceeded a threshold network usage that indicates a price at which the CDN service provider to provide content on behalf of the content provider. Using both or either of these thresholds, the CDN service provider can further process the DNS query by providing an alternative resource identifier or a cache IP address, both associated with an alternative POP. In some embodiments, the CDN service provider determines a routing mode for the response to the DNS query.

BACKGROUND

Generally described, computing devices and communication networks can beutilized to exchange information. In a common application, a computingdevice can request content from another computing device via thecommunication network. For example, a user at a personal computingdevice can utilize a software browser application to request a Web pagefrom a server computing device via the Internet. In such embodiments,the user computing device can be referred to as a client computingdevice (“client”) and the server computing device can be referred to asa content provider.

Content providers are generally motivated to provide requested contentto client computing devices often with consideration of efficienttransmission of the requested content to the client computing deviceand/or consideration of a cost associated with the transmission of thecontent. For larger scale implementations, a content provider mayreceive content requests from a high volume of client computing deviceswhich can place a strain on the content provider's computing resources.Additionally, the content requested by the client computing devices mayhave a number of components, which can further place additional strainon the content provider's computing resources.

With reference to an illustrative example, a requested Web page, ororiginal content, may be associated with a number of additionalresources, such as images or videos, which are to be displayed with theWeb page. In one specific embodiment, the additional resources of theWeb page are identified by a number of embedded resource identifiers,such as uniform resource locators (“URLs”). In turn, software on theclient computing devices typically processes embedded resourceidentifiers to generate requests for the content. Often, the resourceidentifiers associated with the embedded resources reference a computingdevice associated with the content provider such that the clientcomputing device would transmit the request for the additional resourcesto the referenced content provider computing device. Accordingly, inorder to satisfy a content request, the content provider would provideclient computing devices data associated with the Web page as well asthe data associated with the embedded resources.

Some content providers attempt to facilitate the delivery of requestedcontent, such as Web pages and/or resources identified in Web pages,through the utilization of a content delivery network (“CDN”) serviceprovider. A CDN server provider typically maintains a number ofcomputing devices in a communication network that can maintain contentfrom various content providers. In turn, content providers can instruct,or otherwise suggest to, client computing devices to request some, orall, of the content provider's content from the CDN service provider'scomputing devices.

As with content providers, CDN service providers are also generallymotivated to provide requested content to client computing devices oftenwith consideration of efficient transmission of the requested content tothe client computing device and/or consideration of a cost associatedwith the transmission of the content. Accordingly, CDN service providersoften consider factors such as latency of delivery of requested contentin order to meet service level agreements or to generally improve thequality of delivery service.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrative of content delivery environmentincluding a number of client computing devices, a content provider, anda content delivery network (CDN) service provider;

FIG. 2 is a block diagram of the content delivery environment of FIG. 1illustrating the registration of a content provider with a CDN serviceprovider;

FIG. 3 is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of a content request from aclient computing device to a content provider;

FIG. 4 is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of a DNS query correspondingto an embedded resource from a client computing device to a CDN serviceprovider;

FIG. 5A is a block diagram of the content delivery environment of FIG. 1illustrating another embodiment of the generation and processing of aDNS query corresponding to an embedded resource from a client computingdevice to a CDN service provider;

FIG. 5B is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of a DNS query correspondingto an alternative resource identifier from a client computing device toanother POP of a CDN service provider;

FIG. 6 is a block diagram of the content delivery environment of FIG. 1illustrating the generation and processing of embedded resource requestsfrom a client computing device to a CDN service provider;

FIG. 7 is a flow diagram illustrative of a POP selection routineimplemented by a CDN service provider;

FIG. 8 is a flow diagram illustrative of a routing mode selectionroutine implemented by a CDN service provider; and

FIG. 9 is a flow diagram illustrative of an alternative POP selectionroutine implemented by a CDN service provider.

DETAILED DESCRIPTION

Generally described, the present disclosure is directed to DNS queryprocessing that provides for the use of various routing modes responsiveto receipt of a DNS query corresponding to a requested resource. Morespecifically, aspects of the disclosure will be described with regard toprocessing resource requests associated with content providers having aflat-rate pricing for use of a CDN service provider's computing devices.In some embodiments, in response to a DNS query corresponding to arequested resource, a CDN service provider may select a less optimal POPto service the requested resource based on one or more criteria andthereby select a “sloppy routing” scheme. For example, the one or morecriteria may correspond to aspects of a flat-rate pricing model offeredto content providers by the CDN service provider to provide content ontheir behalf. Continuing with this example, in such an approach, if acontent provider has exceeded a threshold network usage, which may, forexample, be based at least in part on pricing information for CDNservice provider to provide content on behalf of the content provider,DNS query processing at a DNS server of the CDN service provider caninclude routing a response to the DNS query, in a “sloppy” routingmanner and/or fashion, to a suboptimal POP by determining an alternativeresource identifier or cache IP address at another POP (e.g., located atanother edge server).

Further, aspects of the disclosure will be described with regard to DNSquery processing that can determine a suboptimal, or sloppy, routingapproach to avoid costs associated with data links of cache serversproviding the requested resources. Accordingly, the one or more criteriaused by the CDN service provider may also correspond to aspects of theCDN service provider cost information. More specifically, the datalinks, provisioned by a CDN service provider, can correspond to afinancial cost for the content delivery bandwidth available on the datalinks of the cache servers. This financial cost can be determined inrelation to a threshold content delivery bandwidth. For example, if acurrent content delivery bandwidth exceeds the threshold contentdelivery bandwidth, the CDN service provider incurs greater costs. Invarious embodiments, responses to DNS queries, such as an alternativeresource identifier or a cache IP address, can be sloppy routed toanother POP location with associated data links of cache serversoperating below the threshold content delivery bandwidth.

In one embodiment, the one or more criteria for selecting a “sloppyrouting” scheme includes a latency associated with providing requestedresources for the content provider. In various other embodiments, othercriteria that may affect the selection of sloppy routing for theresponse to a DNS query can include: optimizing content accessibilityvia hashing algorithms, security concerns, favoring certain contentproviders (e.g., customers), or favoring certain content uses.

Still further, aspects of the disclosure will be described with regardto DNS query processing for sloppy routing schemes using one or morecriteria. The one or more criteria may include both the thresholdnetwork usage and the threshold content delivery bandwidth. For example,in such multi-criterion approach, the latency associated with routing aresponse of a DNS query to a suboptimal POP is considered in combinationwith the marginal cost to service a content request at a data linkoperating above the content delivery bandwidth threshold. Accordingly, acontent provider that has exceeded a threshold network usage can berouted in a sloppy manner during a peak time, when other available datalinks of cache servers located at another POP are available at a lowercost or no cost because the data links of those cache servers areoperating under the threshold content delivery bandwidth. Thus, a DNSserver can use the one or more criteria to determine whether to use asuboptimal POP instead of an optimal or original POP.

Further aspects of the disclosure will be described with regard todetermining an appropriate routing mode for providing a requestedresource. In various embodiments, a spectrum of routing modes areavailable to the CDN service provider for use in responding to DNSqueries. The routing modes can include: a default routing mode, a sloppyrouting mode, a regional anycast routing mode, an anycast routing mode,and a “follow-the-moon” routing mode. (The “follow-the-moon” routingmode is described in U.S. patent application Ser. No. 14/229,568, titled“Scaling Computing Instances” and filed on Mar. 28, 2014, the entiretyof which is incorporated herein by reference). The CDN service providermay determine a routing mode for providing a requested resource from aplurality of available routing modes based on one or more criteria. Forexample, the one or more criteria may include the network usageassociated with the content provider, the content delivery bandwidthassociated with the CDN service provider, a susceptibility factorassociated with the content provider, or a latency associated with a POPin providing the requested resource. Additionally or alternatively, theone or more criteria may include one or more susceptibility factorsand/or one or more latencies. For example, in one embodiment, the CDNservice provider may determine that an anycast routing mode isappropriate if a susceptibility factor indicates that the anycastrouting mode is a more appropriate routing mode when providing therequested resource. In another embodiment, the CDN service provider maydetermine that a default routing mode is appropriate if the one or morecriteria indicate that a latency for providing the resource request isto be minimized. After selection of the routing mode, the CDN serviceprovider may provide a response to the DNS query in accordance with thedetermined routing mode.

In another example, a regional anycast routing mode can be determined asthe appropriate routing mode when the one or more criteria indicate thata susceptibility factor (e.g., a security concern) associated with theplurality of available routing modes is higher for a default routingmode, than the regional anycast routing mode. Continuing with thisexample, the response to the DNS query may be routed in accordance withthe regional anycast routing mode so that several cache servers could beused to service the request, thereby enhancing security. In contrast, inthe default routing mode, a cache server can be a single cache server(e.g., an optimal cache server with minimal latency for providing theresource request). Thus, the CDN service provider can provide responsesto DNS queries in accordance with one of a plurality of availablerouting modes based on a variety of criteria.

Although various aspects of the disclosure will be described with regardto illustrative examples and embodiments, one skilled in the art willappreciate that the disclosed embodiments and examples should not beconstrued as limiting.

FIG. 1 is a block diagram illustrative of content delivery environment100 for the management and processing of content requests. Asillustrated in FIG. 1, the content delivery environment 100 includes anumber of client computing devices 102 (generally referred to asclients) for requesting content from a content provider and/or a CDNservice provider. In an illustrative embodiment, the client computingdevices 102 can correspond to a wide variety of computing devicesincluding personal computing devices, laptop computing devices,hand-held computing devices, terminal computing devices, mobile devices,wireless devices, various electronic devices and appliances and thelike. In an illustrative embodiment, the client computing devices 102include necessary hardware and software components for establishingcommunications over a communication network 108, such as a wide areanetwork or local area network. For example, the client computing devices102 may be equipped with networking equipment and browser softwareapplications that facilitate communications via the Internet or anintranet.

The client computing devices 102 may also include necessary hardware andsoftware components for requesting content from network entities in theform of an originally requested resource that may include identifiers totwo or more embedded resources that need to be requested. Further, theclient computing devices 102 may include or be associated with necessaryhardware and software components, such as browser software applications,plugins, scripts, etc., for fulfilling the original resource request andeach embedded resource request. In other embodiments, the clientcomputing devices 102 may be otherwise associated with an external proxyapplication or device, as well as any other additional softwareapplications or software services, used in conjunction with requests forcontent.

Although not illustrated in FIG. 1, each client computing device 102utilizes some type of local DNS resolver component, such as a DNS Nameserver, that generates the DNS queries attributed to the clientcomputing device. In one embodiment, the local DNS resolver componentmay be provided by an enterprise network to which the client computingdevice 102 belongs. In another embodiment, the local DNS resolvercomponent may be provided by an Internet Service Provider (ISP) thatprovides the communication network connection to the client computingdevice 102.

The content delivery environment 100 can also include a content provider104 in communication with the client computing devices 102 via thecommunication network 108. The content provider 104 illustrated in FIG.1 corresponds to a logical association of one or more computing devicesassociated with a content provider. Specifically, the content provider104 can include a web server component 110 corresponding to one or moreserver computing devices for obtaining and processing requests forcontent (such as Web pages) from the client computing devices 102. Thecontent provider 104 can further include an origin server component 112and associated storage component 114 corresponding to one or morecomputing devices for obtaining and processing requests for networkresources from the CDN service provider. One skilled in the relevant artwill appreciate that the content provider 104 can be associated withvarious additional computing resources, such additional computingdevices for administration of content and resources, DNS name servers,and the like. For example, although not illustrated in FIG. 1, thecontent provider 104 can be associated with one or more DNS name servercomponents that would be authoritative to resolve client computingdevice DNS queries corresponding to a domain of the content provider.Although the content delivery environment 100 is illustrated in aclient-server configuration, one skilled in the relevant art willappreciate that the content delivery environment 100 may be implementedin a peer-to-peer configuration as well.

With continued reference to FIG. 1, the content delivery environment 100can further include a CDN service provider 106 in communication with theclient computing devices 102 and the content providers 104 via thecommunication network 108. The CDN service provider 106 illustrated inFIG. 1 corresponds to a logical association of one or more computingdevices associated with a CDN service provider. Specifically, the CDNservice provider 106 can include a number of point of presence (“POP”)locations 116 and 122 that correspond to nodes on the communicationnetwork 108. Each POP 116 and 122 includes a DNS server component 118and 124 made up of a number of DNS server computing devices forresolving DNS queries from the client computers 102. Each POP 116 and122 also includes a resource cache component 120 and 126 made up of anumber of cache server computing devices for storing resources fromcontent providers and transmitting various requested resources tovarious client computers. The DNS server components 118 and 124 and theresource cache components 120 and 126 may further include additionalsoftware and/or hardware components that facilitate communicationsincluding, but not limited, load balancing or load sharingsoftware/hardware components.

In an illustrative embodiment, the DNS server components 118 and 124 andresource cache component 120 and 126 are considered to be logicallygrouped, regardless of whether the components, or portions of thecomponents, are physically separate. Additionally, although the POPs 116and 122 are illustrated in FIG. 1 as logically associated with the CDNservice provider 106, the POPs can be geographically distributedthroughout the communication network 108 to serve the variousdemographics of client computing devices 102. Additionally, one skilledin the relevant art will appreciate that the CDN service provider 106can be associated with various additional computing resources, suchadditional computing devices for administration of content andresources, and the like.

The CDN service provider 106 can further include a routing mode and POPselection service 128, pricing data store 130, and back-end processingservice 132. Illustratively, the routing mode and POP selection service128 can implement various computational, statistical, or machinelearning methods to route the response (e.g., an answer) to a DNS queryreceived at the CDN service provider 106 (e.g., received at DNS servercomponent 118). For example, the routing mode and POP selection service128 can determine an appropriate routing mode for the alternativeresource identifier (e.g., a CNAME) associated with the second DNSserver 124 to the second POP 122 of the CDN service provider 106 or fortthe IP address of a cache component in the resource cache 126 of thesecond POP 122. The routing mode and POP selection service 128 mayinclude different modules or components, which may facilitate orimplement various methods and processes described herein. Further, thesemodules or components may include additional components, systems, andsubsystems for facilitating the methods and processes. Pricing datastore 130 can include pricing information that indicates a price atwhich the CDN provider 106 provides content on behalf of the contentprovider 104. Pricing data store 130 can, additionally or alternatively,include cost information indicating a financial cost of content deliverybandwidth for the CDN service provider 106 (e.g., the costs to operateprovisioned data links at cache servers). For example, in someembodiments, the pricing information can include a flat-rate price formonthly service for the content provider 104 by CDN provider 106.

Illustratively, back-end processing service 132 can include a number ofhardware and software components. More specifically, the back-endprocessing service 132 may include hardware, software, configurationdata, data structures, computer-readable code, or any type ofinformation that can be loaded into memory and processed by back-endprocessing service 132. Aspects of the back-end processing service 132will be described in further detail below with respect to FIG. 4 thatillustrates the processing and storing service provided by back-endprocessing service 132. In various embodiments, reference to the routingmode and POP selection service 128 and back-end processing service 132within the present disclosure may include multiple computing devicesworking in conjunction to facilitate the selecting of alternativeresource identifiers or cached IP addresses at alternative POP locationsto service content requests. For example, in various embodiments, therouting mode and POP selection service 128 may be distributed through anetwork or implemented by one or more virtual machine instances.Additionally or alternatively, it can be appreciated by one skilled inthe art that the routing mode and POP selection service 128 and back-endprocessing service 132 may correspond to a combination thereof and/orinclude any other services, be centralized in one computing device,and/or be distributed across several computing devices.

With reference now to FIGS. 2-6, the interaction between variouscomponents of the content delivery environment 100 of FIG. 1 will beillustrated. For purposes of the example, however, the illustration hasbeen simplified such that many of the components utilized to facilitatecommunications are not shown. One skilled in the relevant art willappreciate that such components can be utilized and that additionalinteractions would accordingly occur without departing from the spiritand scope of the present disclosure.

With reference to FIG. 2, an illustrative interaction for registrationof a content provider 104 with the CDN service provider 106 will bedescribed. As illustrated in FIG. 2, the CDN content registrationprocess begins with registration of the content provider 104 with theCDN service provider 106. In an illustrative embodiment, the contentprovider 104 utilizes a registration application program interface(“API”) to register with the CDN service provider 106 such that the CDNservice provider 106 can provide content on behalf of the contentprovider 104. The registration API includes the identification of theorigin server 112 of the content provider 104 that will providerequested resources to the CDN service provider 106.

One skilled in the relevant art will appreciate that upon identificationof appropriate origin servers 112, the content provider 104 can begin todirect requests for content from client computing devices 102 to the CDNservice provider 106. Specifically, in accordance with DNS routingprinciples, a client computing device request corresponding to aresource identifier would eventually be directed toward a POP 116 and122 associated with the CDN service provider 106. In the event that theresource cache component 120 and 126 of a selected POP does not have acopy of a resource requested by a client computing device 102, theresource cache component will request the resource from the originserver 112 previously registered by the content provider 104.

With continued reference to FIG. 2, upon receiving the registration API,the CDN service provider 106 obtains and processes the registrationinformation. In an illustrative embodiment, the CDN service provider 106can then generate additional information that will be used by the clientcomputing devices 102 as part of the content requests. The additionalinformation can include, without limitation, client identifiers, such asclient identification codes, content provider identifiers, such ascontent provider identification codes, executable code for processingresource identifiers, such as script-based instructions, the like. Oneskilled in the relevant art will appreciate that various types ofadditional information may be generated by the CDN service provider 106and that the additional information may be embodied in any one of avariety of formats.

The CDN service provider 106 returns an identification of applicabledomains for the CDN service provider (unless it has been previouslyprovided) and any additional information to the content provider 104. Inturn, the content provider 104 can then process the stored content withcontent provider specific information. In one example, as illustrated inFIG. 2, the content provider 104 translates resource identifiersoriginally directed toward a domain of the origin server 112 to a domaincorresponding to the CDN service provider. The translated URLs areembedded into requested content in a manner such that DNS queries forthe translated URLs will resolve to a DNS server corresponding to theCDN service provider 106 and not a DNS server corresponding to thecontent provider 104. Although the translation process is illustrated inFIG. 2, in some embodiments, the translation process may be omitted in amanner described in greater detail below.

Generally, the identification of the resources originally directed tothe content provider 104 will be in the form of a resource identifierthat can be processed by the client computing device 102, such asthrough a browser software application. In an illustrative embodiment,the resource identifiers can be in the form of a uniform resourcelocator (“URL”). Because the resource identifiers are included in therequested content directed to the content provider 104, the resourceidentifiers can be referred to generally as “content provider URLs.” Forpurposes of an illustrative example, a content provider URL can identifya domain of the content provider 104 (e.g., contentprovider.com), a nameof the resource to be requested (e.g., “resource.xxx”) and a path wherethe resource will be found (e.g., “path”). In this illustrative example,the content provider URL has the form of:

-   -   http://www.contentprovider.com/path/resource.xxx

During an illustrative translation process, the content provider URL ismodified such that requests for the resources associated with thetranslated URLs resolve to a POP associated with the CDN serviceprovider 106. In one embodiment, the translated URL identifies thedomain of the CDN service provider 106 (e.g., “cdnprovider.com”), thesame name of the resource to be requested (e.g., “resource.xxx”) and thesame path where the resource will be found (e.g., “path”). Additionally,the translated URL can include additional processing information (e.g.,“additional information”). The translated URL would have the form of:

-   -   http://additional_information.cdnprovider.com/path/resources.xxx

In another embodiment, the information associated with the CDN serviceprovider 106 is included the modified URL, such as through prepending orother techniques, such that the translated URL can maintain all of theinformation associated with the original URL. In this embodiment, thetranslated URL would have the form of:

-   -   http://additional_information.cdnprovider.com/www.contentprovider.com/path/resource.xxx

With reference now to FIG. 3, after completion of the registration andtranslation processes illustrated in FIG. 2, a client computing device102 subsequently generates a content request that is received andprocessed by the content provider 104, such as through the Web server110. In accordance with an illustrative embodiment, the request forcontent can be in accordance with common network protocols, such as thehypertext transfer protocol (“HTTP”). Upon receipt of the contentrequest, the content provider 104 identifies the appropriate responsivecontent. In an illustrative embodiment, the requested content cancorrespond to a Web page that is displayed on the client computingdevice 102 via the processing of information, such as hypertext markuplanguage (“HTML”), extensible markup language (“XML”), and the like. Therequested content can also include a number of embedded resourceidentifiers, described above, that corresponds to resource objects thatshould be obtained by the client computing device 102 as part of theprocessing of the requested content. The embedded resource identifierscan be generally referred to as original resource identifiers ororiginal URLs.

Upon receipt of the requested content, the client computing device 102,such as through a browser software application, begins processing any ofthe markup code included in the content and attempts to acquire theresources identified by the embedded resource identifiers. Accordingly,the first step in acquiring the content corresponds to the issuance, bythe client computing device 102 (through its local DNS resolver), of aDNS query for the original URL resource identifier that results in theidentification of a DNS server authoritative to the “.” and the “com”portions of the translated URL. After resolving the “.” and “com”portions of the embedded URL, the client computing device 102 thenissues a DNS query for the resource URL that results in theidentification of a DNS server authoritative to the “.cdnprovider”portion of the embedded URL. The issuance of DNS queries correspondingto the “.” and the “com” portions of a URL are well known and have notbeen illustrated.

With reference now to FIG. 4, in an illustrative embodiment, aftercompletion of the registration and translation processes illustrated inFIG. 2, the successful resolution of the “cdnprovider” portion of theoriginal URL identifies a network address, such as an IP address, of aDNS server component 118 associated with the CDN service provider 106.In one embodiment, the IP address is a specific network address uniqueto a DNS server component 118 of POP 116. In another embodiment, the IPaddress can be shared by one or more POPs 116, 122. In this embodiment,a DNS query to the shared IP address utilizes a one-to-many networkrouting schema, such as anycast, such that a specific POP, POP 118, willreceive the request as a function of network topology. For example, inan anycast implementation, a DNS query issued by a client computingdevice 102 to a shared IP address will arrive at a DNS server componentlogically having the shortest network topology distance, often referredto as network hops, from the client computing device. The networktopology distance does not necessarily correspond to geographicdistance. However, in some embodiments, the network topology distancecan be inferred to be the shortest network distance between a clientcomputing device 102 and a POP.

With continued reference to FIG. 4, in either of the above-identifiedembodiments (or any other embodiment), a specific DNS server in the DNScomponent 118 of a POP 116 receives the DNS query corresponding to theoriginal URL from the client computing device 102. Once one of the DNSservers in the DNS component 118 receives the request, the specific DNSserver attempts to resolve the request. In an illustrative embodiment, aspecific DNS server can resolve the DNS query by selecting an IP addressof a resource cache component that will process the request for therequested resource. Alternatively, in another embodiment, as will bedescribed further below in reference to FIGS. 5A and 5B, an alternativeresource identifier (e.g., a CNAME) associated with another DNS servercomponent of the CDN service provider 106 may be selected and returnedto the client computing device 102. In either case, as will also befurther described below, the CDN service provider 106, can implementvarious methods and systems to select a routing mode for an IP addressof a cache server component of the CDN service provider 106 or analternative resource identifier associated with another DNS servercomponent of the CDN service provider 106, such as via the routing modeand POP selection service 128 as generally discussed above.

Returning to the embodiment of FIG. 4 specifically, the DNS servercomponent 118 processes the DNS query in part by selecting an IP addressof a resource cache component of the CDN service provider 106 based atleast in part on one or more criteria. The one or more criteria caninclude aspects of a flat-rate pricing model offered by the CDN serviceprovider 106 and aspects of a CDN service provider cost information.Accordingly, a threshold network usage and a threshold content deliverybandwidth can be used as one or more criteria during DNS queryprocessing to select an IP address of the resource cache component. Toevaluate these thresholds, the data links of the resource cachecomponents 120 and 126 are associated with a throughput capability thatcan be measured. For example, the throughput capability of one data linkat a single cache server of resource cache component 120 (orcollectively as several data links at resource cache components 120 and126) can include a measurement of the available bandwidth, usedbandwidth (e.g., network usage), or other metrics that may evaluate theperformance of networked components such as data links associated withresource cache components. In some instances, these measurements ofbandwidth can be evaluated as a percentile (e.g., a 95th percentilemetric) with reference to other data links at a specific resource cachecomponent or several resource cache components, aggregated to use as astatistical metric. With these metrics, the DNS server component 118then processes the DNS query in part with reference to these metrics anddetermines whether a sloppy routing scheme may be used if a certainmetric falls above or below a certain threshold (e.g., a thresholdnetwork usage of content provider 104). Accordingly, various one or morecriteria corresponding to metrics of the data links at the resourcecache components 120 and 126 may be used to determine whether a sloppyrouting scheme should be used.

In one embodiment of sloppy routing using the CDN service provider costinformation as the one or more criteria, the routing mode and POPselection service 128 of the CDN service provider 106 can determine toroute the response to a DNS query (e.g., a content request) to adifferent DNS server associated with an alternative resource identifieror a cache IP address that, in this example, is not the optimal servicelocation for that DNS query. In various embodiments, the CDN serviceprovider 106 can determine a suboptimal routing approach to avoid costsassociated with data links of the resource cache components 120 and 126servicing the content requests. In this approach, the CDN serviceprovider 106 can provision the data links (e.g., hardware) necessary atthe resource cache components 120 and 126 based on the available contentdelivery bandwidths of the resource cache components 120 and 126 or theDNS query processing of DNS server components 118 and 124 for servicingthe requested resources. These data links, not illustratively depictedin FIG. 3, operating via network 108 cost the CDN service provider 106,in various embodiments, on a per data link basis. The costs of thesedata links may vary in various scenarios. In some embodiments, the costof the data links can be determined based on the DNS query processing ofthe DNS server components 118 and 124 or the available content deliverybandwidth at resource cache components 120 and 126. The DNS servercomponents 118 and 124 and resource cache components 120 and 126 can belocated on edge servers at the POPs 116 and 122 located within network108.

More specifically, the cost of these data links at resource cachecomponents 120 and 126 can correspond to a threshold content deliverybandwidth for a particular data link (or all of the data links). In anillustrative example, the CDN service provider 106 may incur anadditional cost when a data link at the DNS server component 118 is usedat a 95th percentile capacity of request handling at one or more cacheservers of resource cache component 120 for a certain period of timecorresponding to a time bucket. Time buckets may be used to determinethe cost of operating the cache server above the threshold contentdelivery bandwidth. For example, a five-minute time bucket of operatingabove the threshold content delivery bandwidth can correspond to acertain cost; a thirty-minute time bucket, an even higher cost. If, onthe other hand, the request handling at one or more cache servers ofresource cache component 120 operates below that percentile, the CDNservice provider 106 may incur no cost or a lesser cost. Thus the CDNservice provider 106 can route various content requests to differentdata links of alternative cache servers (e.g., cache servers at resourcecache component 126) based on the request handling capacity at cacheservers of resource cache component 120 operating below or above thatcost percentile. In another illustrative example, if the data link atresource cache component 120 is operating at the 98th percentile, theCDN service provider 106 can determine that another resource cachecomponent 126, operating only at a 50th percentile, may be includealternative cache servers to handle the content requests because eventhis rerouted content request only raises the request handling at thecache servers of resource cache component 126 to the 55th percentile.With this rerouting approach, eventually, the overloaded 98 percentiledata link at resource cache component 120 may fall below the threshold,for example, now operating at the 90th percentile. With this approach,the CDN service provider 106 has now lowered its cost operating belowthe threshold content delivery bandwidth at both data links of resourcecache components 120 and 126. This can be referred to as a sloppyrouting mode. In this continued example, the CDN service provider 106can determine an alternative DNS server associated with an alternativeresource identifier (as depicted in FIGS. 5A and 5B) or a cache IPaddress (as depicted in FIG. 4), both at an alternative POP, where theresponses to the DNS queries can be routed. In some embodiments, thethreshold content delivery bandwidth (e.g., the cost percentile at whichthe CDN service provider 106 incurs costs) can be stored in the pricingdata store 130. The corresponding time buckets at which the CDN serviceprovider 106 incurs costs operating above the threshold content deliverybandwidth can also be stored in the pricing data store 130. Thethreshold content delivery bandwidth of data links at cache servers cancorrespond to peak request handling for resource cache components (e.g.,cache servers).

In various embodiments, the CDN service provider 106 can use theback-end processing service 132 to process stored historical data todetermine whether a particular POP exceeds the threshold contentdelivery bandwidth during regular daily intervals, seasonally, or on amonthly basis. Back-end processing service 132 may use various methodsassociated with DNS query processing to track the DNS query at DNSservers or the content delivery bandwidth of data links associated withthe resource cache components, located at various POPs (e.g., on edgeservers) connected via the network 108.

In another illustrative example of sloppy routing, the CDN serviceprovider 106 can determine to route the response of a DNS query (e.g., acontent request) to a cache IP address that is not the optimal locationfor that content request because the content provider 104 has exceeded athreshold network usage. The CDN service provider 106 can determine apricing structure for the content provider 104; for example, the contentprovider 104 can be charged a flat-rate price for network usage. Thismay allow the content provider 104 to determine that the CDN serviceprovider 106 is cost efficient because a flat rate price is charged fornetwork bandwidth. However with this predictability, the content serviceprovider 106 can determine that some content providers exceed theirthreshold network usage that has been predicted corresponding to adetermined flat-rate price. When the content provider 104 has exceededthe flat-rate price, the CDN service provider 106 can use a sloppyrouting approach to reroute content requests to a suboptimal location.In some embodiments, this approach provides a balanced or reasonablelatency: not the optimal latency in a default routing approach thatdetermines the optimal cache IP address to service a DNS query, but alsonot the worst latency that a content provider 104 might find using ananycast routing approach. Thus the sloppy routing mode, in theseembodiments, balances the latency for the content provider 104 (e.g., acustomer) with the flat-rate price that the content provider 104 haspaid for a corresponding network usage at that flat-rate price. In oneembodiment, the content provider 104 can be on a monthly network usageplan: The content provider 104 is routed to the optimal location in thedefault routing approach; but, once the customer has exceeded thethreshold network usage for the month, the routing mode and POPselection service 128 determines that the sloppy routing mode can beused to route a response to an alternative DNS server (which may beidentified with an alternative resource identifier as depicted in FIG.5A) or an IP address of a resource cache component at another POPlocation (e.g., the resource cache 126 at the second POP 122 as depictedin FIG. 3). In another embodiment, once the content provider 104 hasexceeded the threshold network usage, the content provider 104 may bererouted automatically for a specific time of day to an alternative DNSserver (e.g., the DNS server 124) or an IP address of a cache componentat another POP location. For example, multiple content requests formovies at 8 p.m. on Friday night can be rerouted to a suboptimallocation, if that specific content provider 104 has already exceededtheir threshold network usage for that month.

In various embodiments, the back-end processing service 132 can retrievefrom pricing data store 130 various prices for the content provider 104and costs of the CDN service provider 106. With this data, the back-endprocessing service 132 can process the tracked behavior of the networkusage for the content provider 104 with various monitoring mechanismsand/or approaches used by the CDN service provider 106. For example, theCDN service provider 106 may keep records of the network usage ofvarious content providers 104 on a daily basis. In various otherapproaches, the CDN service provider 106 can store the pricing structurefor various content providers 104 in the pricing data store 130. Forexample, the pricing structure can include a graduated pricing structurefor a new customer (e.g., another content provider 104) or a discountedpricing structure for a loyal customer (e.g., another content provider104). Using both the pricing data store 130 and the back-end processingservice 132, the CDN service provider 106 can determine the networkusage of various content providers 104.

In another illustrative example, the DNS server component 118 may use acombination of the one or more criteria to determine a sloppy routingscheme; for example, using both the threshold content delivery bandwidthand the threshold network usage for the content provider 104. Continuingin this illustrative example, the CDN service provider 106 can determinethat a flat-rate price corresponds to a marginal increase in cost for aparticular data link because that data link corresponds to an optimalrouting approach using DNS. Thus if a content provider 104 has exceededtheir monthly network usage, the CDN service provider 106 can use sloppyrouting to reroute the DNS query to another POP (e.g., either via analternative resource identifier or via a resource cache componentoperated by that POP) that is operating under the cost percentile forthat data link, which corresponds to a threshold content deliverybandwidth. In this combined approach, the CDN service provider 106balances the cost of provisioning subsequent data links against thelatency introduced to the content provider 104 for the use of servicingDNS queries.

In an additional illustrative example of the sloppy routing mode notdepicted in FIG. 4, the DNS server component 118 may keep a list ofavailable IP addresses in the resource cache component 120 correspondingto data links that the CDN service provider 106 is operating. If arequest for content of the content provider 104 is received when contentprovider 104 has exceeded their threshold network usage for a month, DNSserver component 118 can use the list of available IP addresses withtheir corresponding content delivery bandwidth percentiles at thatparticular time. For example, the data link at the first IP address maybe operating at the 98th percentile because, in this example, it is theoptimal IP address, the data link at the second IP address may beoperating at the 94th percentile, and the data link at the third IPaddress may be operating at the 57th percentile. Because, in thisexample, content provider 104 has exceeded their threshold networkusage, the routing mode and POP selection service 128 and back-endprocessing service 132 can determine that the third IP address can beused to service a DNS query; thereby minimizing the cost to operate thedata links of CDN service provider 106. This avoids using the second IPaddress when a marginal increase in DNS queries could push the data linkat the second IP address to operate over the threshold content deliverybandwidth (e.g., the 95th percentile). Additionally, some traffic on thedata link at the second IP address can be routed to the third IP addressif CDN service provider 106 determines that the incremental latencyexperienced is minimal or if the another content provider 104 operatingtheir content requests on the data link at the second IP addresssuddenly exceeds their threshold network usage for the month.

Further in various sloppy routing schemes using a combination of the oneor more criteria, the CDN service provider 106 can determine variouspermutations of the sloppy routing mode based on information regardingthe pricing structure of a content provider 104 stored in the pricingdata store 130. In the same continued example from above, the latencyincurred by a flat-rate price on the data link at the third IP addressmay be a greater cost in terms of latency for the content provider 104when compared to the marginal cost incurred by the CDN service provider106 when servicing that DNS query on the data link at the second IPaddress, which would have resulted in exceeding the threshold contentdelivery bandwidth for the CDN service provider 106. Thus the routingmode and POPs selection service 128 can include a determination thatbalances the latency for the content provider 104 operating above athreshold network usage with the cost incurred by operating a data linkabove the content delivery bandwidth threshold. With this approach inview, various embodiments are possible balancing the latency incurredfor the content provider 104 for a particular cost incurred by CDNservice provider 106. Thus CDN service provider 106 can use a pricingstructure stored in pricing data store 130 for content provider 104 thatis based primarily on the latency that content provider 104 is willingto incur.

Further still, this latency criterion can be related to the use case ofthe content request for that the content provider 104. For example, CDNservice provider 106 can have a pricing structure for content provider104 that charges more for HD video than for public information ortext-based file formats. In some instances, as one of skill in the artcan appreciate, HD video may incur greater latency than files withtext-based formats or emails.

In various embodiments, as one of skill in the art can appreciate, datacan be collected by CDN service provider 106 regarding the contentrequests of the content provider 104 according to time of day, or month,or based on certain content requests. This data can be processed in theback-end processing service 132. All of these factors can be used as theone or more criteria to determine a sloppy routing approach for theresponse of a particular DNS query. Various factors can be processed byback-end processing service 132 as will now be described herein. Forexample, in various embodiments, latency may not be the criterion to beoptimized for sloppy routing, but instead, content accessibility for thecontent provider 104 may be the criterion.

In this sloppy routing approach using content accessibility as one ofthe one or more criteria, the CDN service provider 106 can additionallyuse hashing algorithms to determine a POP location with the lowestlatency to service a particular DNS query. With hashing algorithms, theCDN the service provider 106 can use the routing mode and POP andselection service 128 to divide a certain number of POP into stripes tobe used in computing likelihoods of content availability. Then, ahashing algorithm can use the name of the content provider 104 with theDNS query to determine the likelihood that content is stored for thatcontent provider 104 at a particular POP that would service the resourcerequest with the lowest latency. In this approach, content requests aremore likely to be serviced with less latency by using that POP having ahigher likelihood of content stored at the resource cache component ofthat POP than others. In some embodiments, if the content provider 104includes several requests for the same content, feedback can be used toindicate that any of the POPs may have an equal likelihood of having thecontent stored and thus offer nearly equivalent low latencies.

Additional criteria can be used by routing mode and POP selectionservice 128 during DNS query processing to determine which POP locationsor IP addresses to sloppy route for the response of a particular DNSquery.

Another one or more criteria of sloppy routing include determining POPlocations that can enhance security. In this approach, routing mode andPOP selection service 128 can determine that the second POP 122 is lesssecure so that the list of available IP addresses at the resource cachecomponent 120 no longer includes cache IP addresses associated with thesecond POP 122 or moves the cache IP addresses associated with thesecond POP 122 to the bottom of the list for servicing DNS queries. Morespecifically, routing mode and POP selection service 128 can useinformation that CDN service provider 106 receives from a look-up tableof IP addresses that have security concerns. With this look-up table ofIP addresses, routing mode and POP selection service 128 can comparethat list with the list available of cache IP address for sloppy routingat DNS server component 118 to determine whether a particular IP addressshould be avoided for the content provider 104 that has an increasedsecurity concerns (e.g., an increased susceptibility factor). In someembodiments, this may be additionally addressed by changing the routingmode. For example, the routing mode at routing mode and POP selectionservice 128 can be changed to a regional anycast routing mode or anycastrouting mode for enhanced security. In some embodiments, CDN serviceprovider 106 can financially charge the content provider 104 more toprovide this enhanced security, especially if the content provider 104requests secure connection for content requests (e.g., because contentprovider 104 is servicing DNS queries that include secure or financialtransactions).

Another one or more criteria of sloppy routing include using a favoredor biased approach for a particular content provider 104: the CDNservice provider 106 can determine that a certain content provider 104is favored because it has been a customer of CDN service provider 106for a long period of time (or pays CDN service provider 106 more thanother content providers). In one embodiment then, even though thisfavored or loyal customer has exceeded their threshold network usage,the routing mode and POP selection service 128 can determine thatcontent provider 104 is not sloppy routed, but, instead, contentprovider is provided the optimal IP address at DNS server 118. Incontrast, this favored approach may also be used for new customers. Forexample, a new customer that has only exceeded their threshold at workusage on day 20 of the month could still be provided the optimal IPaddress if the CDN service provider 106 determines that the marginalcost of servicing new customers with a lower latency, even though itincurs a greater cost for the data link, is less than the likelihoodthat new customer may drop coverage or choose another CDN serviceprovider.

With this description, as one of skill in the art can appreciate,various approaches are possible to favor certain content provider 104over another based on preferences determined and processed by back-endprocessing service 132. In some embodiments this may include usinghistorical data to analyze content provider 104 behavior based on:latency, price, security concerns, content accessibility, whether acontent provider 104 is primarily downloading bulk data, whether aparticular POP is a peer of CDN service provider 106 network, or anyother relevant factors that affect servicing a particular DNS query.Further, a combination of factors may be used to determine thealternative resource identifier associated with another POP location orcache IP address to be used when routing a DNS query. For example, CDNservice provider 106 may determine that latency and susceptibilityfactors should be the only factors to be used when selecting a cache IPaddress from the list of available addresses at DNS server 118.

With further reference to FIG. 4, upon selection of a specific cacheserver computing device (or a resource cache component 120, 126), theDNS server component 118 provides an IP address of the cache servercomputing device, resource cache component, or load balancer/load sharedevice associated with a resource cache component. As will be describedfurther below in reference to FIG. 6, the client computing device 102can then utilize Internet communication protocols to request theresource from a specific cache server computing device identified by theIP address. The cache server computing device then processes therequest, as will also be described in greater detail below, to providethe resource to the client computing device 102.

With reference now to FIG. 5A, in another embodiment, after completionof the registration and translation processes illustrated in FIG. 2, aspecific DNS server in the DNS server component 118 of the POP 116receives the DNS query corresponding to the original URL from the clientcomputing device 102. Once one of the DNS servers in the DNS servercomponent 118 receives the request, the specific DNS server attempts toresolve the request. In one illustrative embodiment, as described aboveand shown in reference to FIG. 4, a specific DNS server resolves the DNSquery by identifying an IP address of a cache server component that willprocess the request for the requested resource. As described above andas will be described further below in reference to FIG. 6, a selectedresource cache component can process the request by either providing therequested resource if it is available or attempt to obtain the requestedresource from another source, such as a peer cache server computingdevice or the origin server 112 of the content provider 104.

Returning to FIG. 5A, as an alternative to selecting a resource cachecomponent upon receipt of a DNS query as described in reference to FIG.4, the CDN service provider 106 can process the DNS query to selectanother POP for further processing a subsequent DNS query associatedwith the originally requested resource. The selection of another POP canalso be based, at least in part, on the same one or more criteriadetailed above with respect the selection of a resource cache componentin FIG. 4. In this embodiment, the CDN service provider 106 can maintainsets of various alternative resource identifiers. The alternativeresource identifiers can be provided by the CDN service provider 106 tothe client computing device 102 such that a subsequent DNS query on thealternative resource identifier will be processed by a different DNSserver component within the CDN service provider's network. In anillustrative embodiment, the alternative resource identifiers are in theform of one or more canonical name (“CNAME”) records. In one embodiment,each CNAME record identifies a domain of the CDN service provider 106(e.g., “cdnprovider.com” or “cdnprovider-1.com”). As will be explainedin greater detail below, the domain in the CNAME does not need to be thesame domain found in original URL or in a previous CNAME record.Additionally, each CNAME record includes additional information, such asrequest routing information, (e.g., “request routing information”). Anillustrative CNAME record can have the form of:

-   -   http://request_routing_information.cdnprovider.com/path/resource.xxx        CNAME request_routing_information.cdnprovider.com

In an illustrative embodiment, the CNAME records are generated andprovided by the DNS servers to direct a more appropriate DNS server ofthe CDN service provider 106. As used in accordance with the presentdisclosure, appropriateness can be defined in any manner by the CDNservice provider 106 for a variety of purposes. In an illustrativeembodiment, as will be described in greater detail below in reference toFIG. 7, in addition to the one or more criteria noted above, the CDNservice provider 106 can utilize domain information associated with thecontent provider 104, at least in part, to identify the more appropriateDNS server of the CDN service provider 106. In particular, the CDNservice provider 106 can use the domain information in the DNS query toidentify the content provider 104, and in turn, identify a current andthreshold network usage for the identified content provider 104. Asnoted above, the threshold network usage for a content provider can bedetermined based, at least in part, on pricing information for the CDNservice provider to provide content on behalf of the content provider104. Specifically, as one example, a content provider may pay a flat feefor unlimited network usage of the CDN service provider's network.However, the CDN service provider 106 may manage its resources bydetermining a threshold network usage for the content provider based onits flat fee at or below which the CDN service provider 106 will processrequests at an optimal POP or route requests to an optimal POP.Alternatively, if the current network usage for servicing domainscorresponding to the content provider 104 is above the threshold networkusage, the CDN service provider 106 can select a less optimal POP toprocess the request.

In another embodiment, building on the foregoing example, the CDNservice provider 106 can utilize client location information associatedwith the client computing device 102 or its local DNS resolver, at leastin part, to identify the more appropriate DNS server of the CDN serviceprovider 106. In particular, the CDN service provider 106 can utilize anIP address associated with a client computing device DNS query toidentify a best sub-optimal POP to process the request. Based on theclient location information, the CDN service provider 106 can thenselect a POP 116, 122 from a set of sub-optimal POPs that are identifiedas being available to service resource requests under the circumstances.In one example, if more than one POP is identified in the set ofsub-optimal POPs, the CDN service provider 106 can utilize adistribution allocation for selecting a specific POP associated with theclient location information. In another example, once a POP is selected,the CDN service provider 106 can further use health information todetermine whether the selected POP is available to service requestsbefore providing the client computing device with a CNAME correspondingto the selected POP. This health information may in one embodimentcorrespond to a threshold content delivery bandwidth available at thePOP as also described above. One skilled in the art will appreciate thatthe above functionality is illustrative in nature and accordingly shouldnot be construed as limiting.

As described above, in addition to the consideration of client locationinformation (either of the end-client or its associated local DNSresolver component), the CDN service provider 106 can utilize theadditional information (e.g., the “additional information”) included inthe translated URL to select a more appropriate DNS server. In oneaspect, the CDN service provider 106 can utilize the additionalinformation to select from a set of DNS servers identified as satisfyingcriteria associated with the client location information or from a setof DNS services identified as satisfying any other criterion orcombination of criteria, such as those described in other exampleembodiments herein. In another aspect, the CDN service provider 106 canutilize the additional information to validate the DNS server selectedin accordance with the client location information or to select analternative DNS server previously selected in accordance with the clientlocation information. In one example, the CDN service provider 106 canattempt to direct a DNS query to DNS servers according to additionalgeographic criteria. The additional geographic criteria can correspondto geographic-based regional service plans contracted between the CDNservice-provider 106 and the content provider 104 in which various CDNservice provider 106 POPs are grouped into geographic regions.Accordingly, a client computing device 102 DNS query received in aregion not corresponding to the content provider's regional plan may bebetter processed by a DNS server in region corresponding to the contentprovider's regional plan. In another example, the CDN service provider106 can attempt to direct a DNS query to DNS servers according toservice level criteria. The service level criteria can correspond toservice or performance metrics contracted between the CDN serviceprovider 106 and the content provider 104. Examples of performancemetrics can include latencies of data transmission between the CDNservice provider POPs and the client computing devices 102, total dataprovided on behalf of the content provider 104 by the CDN serviceprovider POPs, error rates for data transmissions, and the like.

In still a further example, the CDN service provider 106 can attempt todirect a DNS query to DNS servers according to network performancecriteria. The network performance criteria can correspond tomeasurements of network performance for transmitting data from the CDNservice provider POPs to the client computing device 102. Examples ofnetwork performance metrics can include network data transfer latencies(measured by the client computing device or the CDN service provider106, network data error rates, and the like).

In accordance with an illustrative embodiment, the DNS server maintainsa data store that defines CNAME records for various original URLs. If aDNS query corresponding to a particular original URL matches an entry inthe data store, the DNS server component 118 returns a CNAME record asdefined in the data store. In an illustrative embodiment, the data storecan include multiple CNAME records corresponding to a particularoriginal URL. The multiple CNAME records would define a set of potentialcandidates that can be returned to the client computing device 102. Insuch an embodiment, the DNS server component 118, either directly or viaa network-based service, can implement additional logic in selecting anappropriate CNAME from a set of possible of CNAMEs. In an illustrativeembodiment, each DNS server component 118, 124 maintains the same datastores that define CNAME records, which can be managed centrally by theCDN service provider 106. Alternatively, each DNS server component 118and 124 can have POP specific data stores that define CNAME records,which can be managed centrally by the CDN service provider 106 orlocally at the POP 116, 122.

Returning to FIG. 5A, one skilled in the relevant art will appreciatethat DNS server component 118 may select (or otherwise obtain) a CNAMErecord that is intended resolve to a more appropriate DNS server of theCDN service provider 106 based one or more criteria, as described above.Then, the CDN service provider 106 returns the CNAME record to theclient computing device 102.

With reference now to FIG. 5B, upon receipt of the CNAME from the DNSserver component 118, the client computing device 102 generates asubsequent DNS query corresponding to the CNAME. As previously discussedwith regard to FIG. 5A, the DNS query process could first start with DNSqueries for the “.” and “com” portions, followed by a query for the“cdnprovider” portion of the CNAME. To the extent, however, that theresults of a previous DNS queries can be cached (and remain valid), theclient computing device 102 can utilize the cached information and doesnot need to repeat the entire process. However, at some point, dependingon whether the CNAME provided by DNS server component 118 (FIG. 5A) andthe previous URL or CNAME share common CDN service provider domains, thecurrent CNAME DNS query will be processed by a different POP provided bythe CDN service provider 106. As illustrated in FIG. 5B, the DNS servercomponent 124 of POP 122 receives the current CNAME based on thedifferent information in the current CNAME previously provided by theDNS server component 118. As previously described, the DNS servercomponent 124 can then determine whether to resolve the DNS query on theCNAME with an IP address of a cache component that will process thecontent request or whether to provide another alternative resourceidentifier selected in the manners described above.

For purposes of illustration, assume that the DNS server component 124processes the content request by returning an IP address of a resourcecache component. In an illustrative embodiment, the DNS server component124 can utilize a variety of information in selecting a resource cachecomponent. In one example, the DNS server component 124 can default to aselection of a resource cache component of the same POP. In anotherexample, the DNS server components can select a resource cache componentbased on various load balancing or load sharing algorithms. Stillfurther, the DNS server components can utilize network performancemetrics or measurements to assign specific resource cache components.The IP address selected by a DNS server component may correspond to aspecific caching server in the resource cache. Alternatively, the IPaddress can correspond to a hardware/software selection component (suchas a load balancer).

With reference now to FIG. 6, continuing with an illustrative embodimentcorresponding to FIGS. 5A and 5B, assume that the DNS server component124 shown in FIG. 5B has selected the default resource cache component126 of the POP 122. Upon receipt of the IP address for the resourcecache component 126, the client computing device 102 transmits, as shownin FIG. 6, a request for the requested content to the resource cachecomponent 126. The resource cache component 126 processes the request ina manner described above and the requested content is transmitted to theclient computing device 102.

Alternatively, in another embodiment corresponding to FIG. 4, assumethat the DNS server component 118 has selected a specific resource cachecomponent of another POP, such as POP 122 based on the one or morecriteria as described above. Upon receipt of the IP address for theresource cache component 126 of the POP 122, the client computing device102 transmits, as shown in FIG. 6, a request for the requested contentto the resource cache component 126. The resource cache component 126processes the request in a manner described above and the requestedcontent is transmitted to the client computing device 102.

A selected resource cache component (either selected directly by a POPreceiving a DNS query as shown in FIG. 4 or as a default upon selectionof an alternative POP via an alternative resource identifier as shown inFIGS. 5A and 5B) can process the request by either providing therequested resource if it is available or obtaining the requestedresource from another source, such as a peer cache server computingdevice or the origin server 112 of the content provider 104.

With reference now to FIG. 7, one embodiment of a POP selection routine702 implemented by the CDN provider 106 will be described. One skilledin the relevant art will appreciate that actions/steps outlined forroutine 702 may be implemented by one or many computingdevices/components that are associated with the CDN service provider106. Accordingly, routine 702 has been logically associated as beinggenerally performed by the CDN service provider 106, and thus thefollowing illustrative embodiments should not be construed as limiting.

At block 704, a DNS server component 118 at a first POP 116 of the CDNservice provider 106 receives a DNS query corresponding to a resourceidentifier from a client computing device 102. As previously discussed,the resource identifier can be a URL that has been embedded in contentrequested by the client computing device 102 and previously provided bythe content provider 104. Alternatively, the resource identifier canalso correspond to a CNAME provided by a content provider DNS server inresponse to a DNS query previously received from the client computingdevice 102. While not illustrated, the receiving DNS server alsoobtains, in some embodiments, an IP address associated with the DNSquery from the requesting client computing device 102 (“query IPaddress”). The query IP address can correspond to an IP address of theclient computing device or any local DNS resolver component associatedwith the client computing device.

Next, at decision block 706, the CDN service provider 106 determineswhether it has exceeded a threshold content delivery bandwidth at thefirst POP. As discussed above, the threshold content delivery bandwidthis determined based, at least in part, on CDN service provider costinformation, which corresponds to a financial cost to the CDN serviceprovider 106 for content delivery bandwidth. In particular, in oneembodiment, assuming that the first POP, or more specifically the DNSserver component at the first POP, receiving the DNS query is theoptimal POP or DNS server component for processing the DNS query, thisdetermination at block 706 corresponds to a determination of whether theresource cache component at the POP receiving the DNS query (which cancorrespond to either a single cache server or a bank of cache servers atthe POP) is operating above a threshold content delivery bandwidth.Continuing with this embodiment, the resource cache component at thefirst POP can also be referred to as the default or optimal resourcecache component. In a further illustrative embodiment, the thresholdcontent delivery bandwidth is lower than a maximum available contentdelivery bandwidth for the first POP or resource cache component.

If the first POP or resource cache component has not exceeded itsthreshold content delivery bandwidth, the CDN service provider 106responsively provides the client computing device 102 with an IP addressof the default or optimal resource cache component at the first POP atblock 708. Thereafter, at block 716, routine 702 ends. Alternatively, ifat decision block 706, the first POP or resource cache component hasexceeded its threshold content delivery bandwidth (which may beindicative, for example, of the CDN service provider 106 incurringadditional financial costs to provide the requested content from thefirst POP or its default resource cache component), the CDN serviceprovider 106 determines whether a content provider corresponding to adomain associated with the DNS query has exceeded a threshold networkusage at block 710.

If the content provider has not exceeded its threshold network usage,the CDN service provider 106 responsively provides the client computingdevice 102 with an IP address of the default or optimal resource cachecomponent of the first POP at block 710. Thereafter, at block 716,routine 702 ends. Alternatively, if at decision block 710, the contentprovider has exceeded its threshold network usage (which may beindicative, for example, of the CDN service provider incurring theburden of additional financial costs above a pricing structure, such asa flat fee structure, offered to the content provider), processingcontinues at block 712. As described above, in an illustrativeembodiment, the threshold network usage is determined based, at least inpart, on pricing information for the CDN provider to provide content onbehalf of the content provider.

While the routine 702 illustrates making both determinations at blocks706 and 710, in another embodiment, the determination at block 706 maybe optional, while in a yet further alternative embodiment, thedetermination at block 710 may be optional.

Continuing at block 712, if either or both of the determinations atblocks 706 and 710 result in a “YES” determination, the CDN serviceprovider 106 selects an alternative resource identifier associated withan alternative POP of the CDN service provider 106 or an alternativecache IP address associated with an alternative POP. In particular, inone illustrative embodiment, where an alternative resource identifier isselected, the CDN service provider 106 more specifically selects analternative resource identifier which would resolve to a particularalternative DNS server at the alternative POP. In another illustrativeembodiment, where an alternative cache IP address is selected, the CDNservice provider 106 may select an alternative cache IP address for aparticular cache server of a resource cache component at the alternativePOP or generally for a group of cache servers at the alternative POP. Inthis way, the CDN service provider 106 directs further processing of therequest to an alternative POP of the CDN service provider.

Next, at block 714, the selected alternative resource identifier oralternative cache IP address is transmitted to the client in response tothe obtained DNS query for further processing. Thereafter, at block 716,routine 702 ends. In various embodiments, routine 702 may be performedby the CDN service provider 106 generally, or by DNS server components118, 124 or individual DNS servers associated with the DNS servercomponents 118,124. The CDN service provider 106, DNS server components118, 124, or individual DNS servers associated with the DNS servercomponent 118, 124 may themselves include or otherwise access a serviceto implement the routine 702, such as the routing mode and POP selectionservice 128 of FIG. 1. In other embodiments, a physical computing devicewith computer executable instructions may cause the computing device toperform routine 702. In some embodiments of the routine 702, elementsmay occur in sequences other than as described above. In addition, asnoted above, some elements of the routine may be optional, such as thedeterminations at either block 706 or 710. One skilled in the art willappreciate that additional variations are possible and within the scopeof the present disclosure.

With reference now to FIG. 8, one embodiment of a routing mode selectionroutine 802 will be described. One skilled in the relevant art willappreciate that actions/steps outlined for routine 802 may beimplemented by one or many computing devices/components that areassociated with the CDN service provider 106. Accordingly, routine 802has been logically associated as being generally performed by the CDNservice provider 106, and thus the following illustrative embodimentsshould not be construed as limiting.

At block 804, a DNS server component 118 at a first POP 116 of the CDNservice provider 106 receives a DNS query corresponding to a resourceidentifier from a client computing device 102. As previously discussed,the resource identifier can be a URL that has been embedded in contentrequested by the client computing device 102 and previously provided bythe content provider 104. Alternatively, the resource identifier canalso correspond to a CNAME provided by a content provider DNS server inresponse to a DNS query previously received from the client computingdevice 102. While not illustrated, the receiving DNS server alsoobtains, in some embodiments, an IP address associated with the DNSquery from the requesting client computing device 102 (“query IPaddress”). The query IP address can correspond to an IP address of theclient computing device or any local DNS resolver component associatedwith the client computing device.

Next, at block 806, the CDN service provider 106 responsively determinesa routing mode for the response to the DNS query obtained at block 804.In some embodiments, this determination can be made during DNS queryprocessing as described above with reference to FIGS. 4-5B. In variousembodiments, a spectrum of routing modes can exist that the CDN serviceprovider 106 may determine during DNS query processing (e.g., at the DNSserver when the DNS query is obtained). A plurality of available routingmodes can include: a default routing mode, a sloppy routing mode, aregional anycast routing mode, and an anycast routing mode. The one ormore criteria used in DNS query processing can be used to determine therouting mode for providing the requested resource. Accordingly, theresponse to the DNS query can be transmitted and/or provided to theclient 102 in accordance with the determined routing mode.

With continuing reference to block 806, the CDN service provider candetermine an appropriate routing mode for providing the requestedresource. As discussed previously with reference to FIG. 4 and inaccordance with the present disclosure, appropriateness can be definedin any manner by the CDN service provider 106 for a variety of purposes.Illustratively, the one or more criteria used to determine the routingmode can include a susceptibility factor (also referred to as securityfactor) and the latency criteria discussed above with reference to FIG.4. In various embodiments, the determination of an appropriate routingmode from a spectrum of routing modes can be based at least in part on atradeoff between a susceptibility factor of a routing mode and thelatency for providing the requested resource with the routing mode. Forexample, in one embodiment, the default routing mode can be determinedas the appropriate routing mode. The determination of the optimal cacheserver may be a default based on the DNS query already being routed tothe optimal POP and received at the DNS server component 118. The DNSserver component 118, then, simply provides an IP address of anassociated cache server at that POP. Alternatively, the DNS servercomponent, upon receiving the DNS query, may be associated with a cacheserver component, and then selects from one of the cache servers ofresource cache component 120 that may be the logically closest.Accordingly, in various embodiments, the default routing mode can alsobe referred to as a latency-based routing mode (e.g., a routing modethat provides an optimal cache server, minimizing latency when providingthe requested resource). Still further, in another embodiment, thislatency-based routing mode can be referred to as a minimal latency-basedrouting mode that minimizes the latency when providing the requestedresources on behalf of the content provider 104. As one of skill in theart can appreciate, these examples illustrate how the default routingmode can offer an optimal cache server at the POP location receiving theDNS query or route the response to a DNS query using a cache IP addressassociated with an optimal cache server. While this optimal cache serverminimizes latency, this default routing mode may, however, provide lesssecurity. But, at the same time, this default routing mode may provideless security because a single specific cache server is typically theoptimal cache server and thus may have a higher susceptibility factorgiven those security concerns. For example, in one embodiment, becausethe optimal cache server is associated with a pre-specified IP address,the specific IP address could be leaked or easily discernible to outsideparties, which raises the security concerns associated with that optimalcache server.

In contrast, the anycast routing mode uses a selected anycast IP address(e.g., a cache IP address or destination IP address) to process resourcerequests. An anycast IP address (e.g., a global IP address that may berandomly assigned to available cache servers) can be associated orshared by several cache servers that can provide the requested resource.Because several cache servers can service the requested resource, thesusceptibility factor of the anycast routing mode is lower than thedefault routing mode. For example, by providing a DNS server componentat the CDN service provider with an option to determine an appropriaterouting mode in which to respond to a DNS query, the DNS servercomponent may select the anycast routing mode to provide enhancedsecurity, as compared to the default routing mode. Such a determinationoffers enhanced security because an original cache server that wouldservice the resource request in a default routing mode can be quicklychanged to a secondary cache server (e.g., another cache server)associated with a shared anycast IP address (e.g., a randomly assignedglobal IP address), if a security concern is discovered to be associatedwith the POP or DNS server component receiving the DNS query, and hencethe original default cache server corresponding to that POP. But, at thesame time, such a secondary cache server can be more geographicallydistant (e.g., traveling through intercontinental optical cables) fromthe client 102, and thus incurring a higher latency, especially whencompared with the default routing mode that uses the optimal cacheserver. In one embodiment, the anycast routing mode, as discussedherein, may correspond to traditional anycast routing as known to thoseof skill in the art.

In another embodiment of determining the appropriate routing mode atblock 806, a content provider can be assigned a susceptibility factorthat relates to the security concerns of each available routing mode.For example, a content provider 104 (e.g., a customer of the CDN serviceprovider 106) that has its content typically served by the CDN serviceprovider 106 in a geographical location (e.g., region with lesssecurity) can have an increased susceptibility factor in a defaultrouting mode. Instead, the anycast routing mode can be determined as theappropriate routing mode to offer enhanced security as an anycast IPaddress is associated with several cache servers via randomly assignedglobal IP address. Thus, in contrast to a specific optimal cache serverassociated with a pre-specified IP address that may be leaked, there aremany available cache servers in the anycast routing mode for providingresponsive content which are not individually designated and hencespecifically targeted. Accordingly, the susceptibility factors may biasthe determination of the appropriate routing mode in favor of theanycast routing mode because the anycast routing mode can provideenhanced security. In contrast, a default cache IP address stored at aDNS server may be more easily discernible as it is individuallypre-designated.

In another example, a regional anycast routing mode can be determined asthe appropriate routing mode, at block 806. In some embodiments, the CDNservice provider 106 may consider the security factor like the anycastrouting mode, but additionally consider the latency factor. This can beundertaken when the one or more criteria indicate that a susceptibilityfactor is to be associated with the plurality of available routingmodes, but also the latency factor associated with the plurality ofavailable routing modes. Continuing in this example, the regionalanycast routing mode can be used to route the response to the DNS queryso that several cache servers are available with a regional IP address(e.g., a regional IP address can be randomly assigned and associatedwith several cache servers in a region) used to service the request,thereby enhancing security. This determination can be made dynamicallyat the DNS server component 118 or it can have been considered by acentral computing component of the CDN service provider 106, which, inturn, provides a list of available cache servers from which the DNSserver component 118 can select from. Thus, the one or more criteria canin part dictate, or de facto, determine a routing mode for providing therequested resource.

In another example, a particular DNS resolver may service a diverse setof client computing devices 102, such as clients that are located inmultiple different geographic regions. Such a resolver is hereinafterreferred to as a diverse DNS resolver. In this example, since theclients are geographically diverse, some clients' resource requests mayexperience more latency than others being serviced by the same DNSresolver. With this information, the CDN service provider 106 maydetermine that a regional anycast routing mode may be the appropriaterouting mode for providing the requested resource at block 806. Theregional anycast routing mode corresponds to a modified version of ananycast routing mode which utilizes a one-to-many network routingschema, but in this instance the one-to-many network routing schema islimited by region, such as a geographic region. In particular, aregional one-to-many network routing schema provides that a specificPOP, DNS server component 118, or resource cache component in aparticular region will receive the request as a function of networktopology in that region. For example, in a regional anycastimplementation, a request issued by a client computing device 102 to ashared IP address will arrive at a POP, DNS server component 118, orresource cache component logically having the shortest network topologydistance, often referred to as network hops, from the client computingdevice. The network topology distance does not necessarily correspond togeographic distance. However, in some embodiments, the network topologydistance can be inferred to be the shortest network distance between aclient computing device 102 and a POP, DNS server component, or resourcecache component.

As a further specific example, the regional anycast routing mode caninvolve the selection of a cache IP address from a grouping or list ofcache IP addresses or anycast node locations that are located within acertain geographical and/or regional location of the nodes (e.g., U.S.East Coast, U.S. West Coast, Canada, or Southeast Asia). In otherembodiments, the CDN service provider 106 can select a cache IP addressfrom a list of IP addresses that are associated with a location of nodesin a region specified by the CDN service provider 106. Accordingly, theCDN service provider 106 can specify certain nodes located in onegeographical area (e.g., U.S. West Coast). In some embodiments, such alist may not include an IP address that is deemed unsecure (e.g., an IPaddress corresponding to a cache server that, due to security concerns,cannot provide requested resources). For example, in some embodiments,financial content such as credit card information may need to be routedwith a routing mode offering higher security. In other embodiments, anunsecure IP address may be an anycast IP address that has been leaked,thereby making security a concern for that particular IP address.

In yet another example of determining the appropriate routing mode atblock 806, the CDN service provider 106 may select a sloppy routingmode. As further described above, a sloppy routing mode can be used toservice content requests from a suboptimal POP if, for example, if theoriginal provider of the specifically requested content (e.g., theoriginal content provider for that content) has exceeded a thresholdnetwork usage or if the CDN service provider 106 has exceeded athreshold content delivery bandwidth at data links of cache serversservicing requests for content originally provided by the contentprovider 104. Accordingly, in various embodiments, the determinedrouting mode can be the sloppy routing mode.

In one embodiment, as described above, the response to a DNS queryutilizing this sloppy routing approach can be either: an alternativeresource identifier (e.g., a CNAME) associated with an alternative DNScomponent at an alternative POP of the CDN service provider or an IPaddress of a resource cache component (e.g., a cache server) at thealternative POP (e.g., second POP 122). In this approach, the responseto the DNS query may be routed to one of several cache servers that maybe available at the alternative POP (or even several alternative POPs).In addition, in this embodiment, because the response to the DNS querymay be routed to one of several cache servers at the alternative POP,the sloppy routing mode can enhance security because several cacheservers are available, rather than one cache server (e.g., the optimalcache server that minimizes latency). In contrast to a default routingmode that may only route the response to a DNS query to one cache server(e.g., a default and/or optimal cache server that can minimize thelatency in providing the requested resource) at the POP that receivedthe DNS query, the slopping routing mode can provide enhanced securityby routing the response to the DNS query to an alternative cache serverat an alternative POP. Further, the sloppy routing mode selection allowsthe CDN service provider 106 to allocate or direct the response of theDNS query within the network of the CDN service provider 106, forexample, to an alternative POP (e.g., second POP 122), which mayminimize latency in servicing the resource request when compared to ananycast routing mode. Thus, the CDN service provider 106 can minimizelatency by analyzing the request handling capacity of alternative POPsavailable to provide the requested resource. Accordingly, a sloppyrouting mode selection can take into account both minimizing the latencywhen providing the requested resource and a susceptibility factor byproviding enhanced security when providing the requested resource.

In various embodiments, information stored in pricing data store 130 canalso be used as the one or more criteria to determine an appropriaterouting mode. For example, one pricing structure may dictate that aflat-rate price is available for the default routing mode, a flat-rateprice is available for the sloppy routing mode, and another flat-rateprice is available for the regional anycast routing mode. Using thisdata from pricing data store 130 and the network usage, the back-endprocessing service 132 can determine whether a content provider 104 hasexceeded their threshold network usage for a particular routing mode ata particular pricing structure. As one of skill in the art canappreciate, various routing modes are available when the one or morecriteria are used in combination with a pricing structure (e.g., a priceat which the CDN service provider 106 provides content on behalf of thecontent provider 104). For example, a content provider 104 can pay morefor the CDN service provider 106 to determine whether a more securerouting mode is available for certain resource requests (e.g., resourcerequests with financial information). In this example, the back-endprocessing service 132 can determine that a regional anycast routingmode is available with less latency than an anycast routing mode, butalso with more security than a default routing mode because thesusceptibility factor of the DNS cache server servicing a particularcontent provider 104 is high.

In addition to the example criteria noted above, the one or morecriteria can also include utilizing information obtained from the DNSquery, at least in part, to identify the more appropriate routing mode.This information may include a domain associated with the contentprovider 104. This information may also include client subnetinformation associated with content provider 104. This information canbe used to determine the routing mode.

Next, at block 808, in response to the obtained DNS query, the selectedalternative resource identifier or selected cache IP address istransmitted to the client in accordance with the determined routingmode. For example, if the determined routing mode is the regionalanycast routing mode, the selected IP cache address (e.g., selected froma list of IP addresses associated with a location of nodes in a regionspecified by the CDN service provider 106) can be provided and/ortransmitted to the client 102 in accordance with the regional anycastrouting mode. Thus, an IP address can be selected that is associatedwith a location of nodes on the US West Coast for example. Thereafter,at block 810, routine 802 ends.

In various embodiments, routine 802 may be performed by the CDN serviceprovider 106 generally, or by DNS server components 118, 124 orindividual DNS servers associated with the DNS server components118,124. The CDN service provider 106, DNS server components 118, 124,or individual DNS servers associated with the DNS server component 118,124 may themselves include or otherwise access a service to implementthe routine 802, such as the routing mode and POP selection service 128of FIG. 1. In other embodiments, a physical computing device withcomputer executable instructions may cause the computing device toperform routine 802. In some embodiments of the routine 802, elementsmay occur in sequences other than as described above. One skilled in theart will appreciate that additional variations are possible and withinthe scope of the present disclosure.

With reference now to FIG. 9, an alternative embodiment of a POPselection routine 902 will be described. One skilled in the relevant artwill appreciate that actions/steps outlined for routine 902 may beimplemented by one or many computing devices/components that areassociated with the CDN service provider 106. Accordingly, routine 902has been logically associated as being generally performed by the CDNservice provider 106, and thus the following illustrative embodimentsshould not be construed as limiting.

At block 904, a DNS server component 118 at a first POP 116 of the CDNservice provider 106 receives a DNS query corresponding to a resourceidentifier from a client computing device 102. As previously discussed,the resource identifier can be a URL that has been embedded in contentrequested by the client computing device 102 and previously provided bythe content provider 104. Alternatively, the resource identifier canalso correspond to a CNAME provided by a content provider DNS server inresponse to a DNS query previously received from the client computingdevice 102. While not illustrated, the receiving DNS server alsoobtains, in some embodiments, an IP address associated with the DNSquery from the requesting client computing device 102 (“query IPaddress”). The query IP address can correspond to an IP address of theclient computing device or any local DNS resolver component associatedwith the client computing device.

Next, at decision block 906, the CDN service provider 106 determineswhether a content provider 104 corresponding to a domain associated withthe DNS query is available. For example, the content provider 104 may beavailable if the content provider 104 has available network usage (e.g.,network usage not exceeding a threshold network usage) or if no securityconcerns exist with providing content of the content provider. However,the content provider 104 may not be available if the content provider104 has exceeded a threshold network usage or if security concerns existregarding the provision of content originally provided by the contentprovider 104. For example, a cache server at the resource cachecomponent 120 that is providing requested resources in accordance with adefault routing mode for the content provider 104 may be unavailable dueto security concerns associated with providing content of the contentprovider 104. In other embodiments, a content provider 104 may bephysically located in a region or location more susceptible to securityconcerns and thus can have an increased susceptibility factor associatedwith the default routing mode. Accordingly, the optimal cache server,physically located in that same region or location, that is providingrequested resources in accordance with a default routing mode for aparticular content provider 104 may be unavailable due to securityconcerns associated with providing content of that particular contentprovider 104. In one embodiment, the CDN service provider 106 candetermine the susceptibility factor for the content provider 104associated with each available routing mode of a plurality of routingmodes. In the depicted alternative embodiment of the POP selectionroutine 902, the available routing modes are: the default routing mode,the sloppy routing mode, and the anycast routing mode.

If the content provider 104 is available (i.e., the CDN service providerdetermines that content originally provided by the content provider 104is available to be provided based on one or more criteria), the CDNservice provider 106, responsive to the DNS query, provides andtransmits to the client computing device 102 an IP address of thedefault or optimal resource cache component of the first POP at block908 in accordance with the default routing mode. In this embodiment, theresource cache component at the first POP can also be referred to as thedefault or optimal resource cache component. Thereafter, at block 918,routine 902 ends. Alternatively, if at decision block 906, the contentprovider is not available, processing continues at decision block 910.

At decision block 910, the CDN service provider 106 determines whetheran alternative POP is available. This decision can include determiningan appropriate routing mode from the remaining available routing modes:the sloppy routing mode and the anycast routing mode. For example, asdescribed above with reference to FIG. 8, an alternative POP may beavailable if a list of IP addresses at the DNS server 118 includesalternative cache IP addresses associated with alternative POPs. If analternative POP is not available (e.g., because the list of IP addressesdoes not include alternative POP locations or cache IP addressesassociated with alternative POPs), at block 912, the CDN serviceprovider 106 responsively provides and transmits to the client computingdevice 102 an IP address in accordance with the anycast routing mode. Inanother embodiment not depicted in FIG. 9, the CDN service provider 106responsively provides and transmits to the client computing device 102an IP address in accordance with the regional anycast routing mode. Inthis embodiment, the IP address can be selected in accordance with thedetermined routing mode as described above with reference to FIG. 8.Thereafter, at block 918, routine 902 ends.

While the routine 902 illustrates making both determinations at blocks906 and 910, in another embodiment, the determination at block 906 maybe optional; while in a yet further alternative embodiment, thedetermination at block 910 may be optional. For example, in variousembodiments, routine 902 can proceed from decision block 906, if thecontent provider is not available, to block 912, where the CDN serviceprovider 106 responsively provides and transmits to the client computingdevice 102 an IP address in accordance with the anycast routing mode.Or, in another optional embodiment not depicted in FIG. 9, the CDNservice provider 106 can responsively provide and transmit to the clientcomputing device 102 an IP address in accordance with the regionalanycast routing mode.

Continuing at block 914, if the content provider is not available atdecision block 906 and an alternative POP is available at block 910, theCDN service provider 106 selects an alternative resource identifierassociated with an alternative POP of the CDN service provider 106 or analternative cache IP address associated with an alternative POP. Inparticular, in one illustrative embodiment, where an alternativeresource identifier is selected, the CDN service provider 106 morespecifically selects an alternative resource identifier which wouldresolve to a particular alternative DNS server at the alternative POP.In another illustrative embodiment, where an alternative cache IPaddress is selected, the CDN service provider 106 may select analternative cache IP address for a particular cache server of a resourcecache component at the alternative POP or generally for a group of cacheservers at the alternative POP. In this way, the CDN service provider106 directs further processing of the request to an alternative POP ofthe CDN service provider.

Next, at block 916, in response to selecting either an alternativeresource identifier or an alternative cache IP address at block 914, theselected alternative resource identifier or alternative cache IP addressis transmitted to the client in response to the obtained DNS query forfurther processing in accordance with the sloppy routing mode.Thereafter, at block 918, routine 902 ends.

In various embodiments, routine 902 may be performed by the CDN serviceprovider 106 generally, or by DNS server components 118, 124 orindividual DNS servers associated with the DNS server components118,124. The CDN service provider 106, DNS server components 118, 124,or individual DNS servers associated with the DNS server component 118,124 may themselves include or otherwise access a service to implementthe routine 902, such as the routing mode and POP selection service 128of FIG. 1. In other embodiments, a physical computing device withcomputer executable instructions may cause the computing device toperform routine 902. In some embodiments of the routine 902, elementsmay occur in sequences other than as described above. In addition, asnoted above, some elements of the routine may be optional, such as thedeterminations at either block 906 or 910. One skilled in the art willappreciate that additional variations are possible and within the scopeof the present disclosure.

Depending on the embodiment, certain acts, events, or functions of anyof the methods described herein can be performed in a differentsequence, can be added, merged, or left out altogether (e.g., not alldescribed acts or events are necessary for the practice of thealgorithm). Moreover, in certain embodiments, acts or events can beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors or processor cores or onother parallel architectures, rather than sequentially.

The various illustrative logical blocks, modules, and method elementsdescribed in connection with the embodiments disclosed herein can beimplemented as electronic hardware, computer software, or combinationsof both. To clearly illustrate this interchangeability of hardware andsoftware, various illustrative components, blocks, modules, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. The described functionality can be implemented invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the disclosure.

The various illustrative logical blocks and modules described inconnection with the embodiments disclosed herein can be implemented orperformed by a machine, such as a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor can be a microprocessor,but in the alternative, the processor can be a controller,microcontroller, or state machine, combinations of the same, or thelike. A processor can also be implemented as a combination of computingdevices, e.g., a combination of a DSP and a microprocessor, a pluralityof microprocessors, one or more microprocessors in conjunction with aDSP core, or any other such configuration.

The elements of a method, process, or algorithm described in connectionwith the embodiments disclosed herein can be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module can reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of computer-readablestorage medium known in the art. A storage medium can be coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium can be integral to the processor. The processor and the storagemedium can reside in an ASIC. The ASIC can reside in a user terminal. Inthe alternative, the processor and the storage medium can reside asdiscrete components in a user terminal.

Conditional language used herein, such as, among others, “can,” “might,”“may,” “e.g.” and the like, unless specifically stated otherwise, orotherwise understood within the context as used, is generally intendedto convey that certain embodiments include, while other embodiments donot include, certain features, elements and/or states. Thus, suchconditional language is not generally intended to imply that features,elements and/or states are in any way required for one or moreembodiments or that one or more embodiments necessarily include logicfor deciding, with or without author input or prompting, whether thesefeatures, elements and/or states are included or are to be performed inany particular embodiment. The terms “comprising,” “including,”“having,” “involving” and the like are synonymous and are usedinclusively, in an open-ended fashion, and do not exclude additionalelements, features, acts, operations and so forth. Also, the term “or”is used in its inclusive sense (and not in its exclusive sense) so thatwhen used, for example, to connect a list of elements, the term “or”means one, some, or all of the elements in the list.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to present that an item, term, etc., may beeither X, Y, or Z, or any combination thereof (e.g., X, Y and/or Z).Thus, such disjunctive language is not generally intended to, and shouldnot, imply that certain embodiments require at least one of X, at leastone of Y or at least one of Z to each be present.

Unless otherwise explicitly stated, articles such as “a” or “an” shouldgenerally be interpreted to include one or more described items.Accordingly, phrases such as “a device configured to” are intended toinclude one or more recited devices. Such one or more recited devicescan also be collectively configured to carry out the stated recitations.For example, “a processor configured to carry out recitations A, B, andC” can include a first processor configured to carry out recitation Aworking in conjunction with a second processor configured to carry outrecitations B and C.

While the above detailed description has shown, described, and pointedout novel features as applied to various embodiments, it will beunderstood that various omissions, substitutions, and changes in theform and details of the devices or algorithms illustrated can be madewithout departing from the spirit of the disclosure. As will berecognized, certain embodiments described herein can be embodied withina form that does not provide all of the features and benefits set forthherein, as some features can be used or practiced separately fromothers. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A computer-implemented method comprising: under control of a hardware computing device configured with specific computer executable instructions: obtaining, at a first domain name system (DNS) server from a client computing device, a first DNS query, wherein a first point of presence (POP) of a content delivery network (CDN) service provider includes the first DNS server, wherein the first DNS query is associated with a requested resource; determining, at the first DNS server, a routing mode from a plurality of available routing modes for providing the requested resource based at least in part on one or more criterion; dynamically selecting, at the first DNS server, (a) an alternative resource identifier associated with a second DNS server at a second POP of the CDN service provider or (b) an IP address of a cache component of the CDN service provider based at least in part on the determined routing mode, wherein the alternative resource identifier includes information for causing a second DNS query to resolve to the second DNS server of the CDN service provider; and transmitting, to the client computing device, the alternative resource identifier or the IP address in accordance with the determined routing mode.
 2. The computer-implemented method of claim 1, wherein the one or more criterion comprises at least one of a susceptibility factor of the content provider, wherein the susceptibility factor is associated with an individual one of the plurality of available routing modes or a latency associated with an individual one of the plurality of available routing modes.
 3. The computer-implemented method of claim 2, wherein the one or more criterion further comprises at least one of a network usage associated with an original content provider or a content delivery bandwidth associated with the CDN service provider, wherein the network usage is based at least in part on content provider pricing information and wherein the content delivery bandwidth is based at least in part on CDN service provider cost information.
 4. The computer-implemented method of claim 1, wherein the determined routing mode is a regional anycast routing mode and wherein the regional anycast routing mode includes a selection of IP addresses associated with one or more network nodes of a region.
 5. A computer-implemented method comprising: under control of a hardware computing device configured with specific computer executable instructions: obtaining, at a first domain name system (DNS) server from a client computing device, a DNS query, wherein a first point of presence (POP) of a content delivery network (CDN) service provider includes the first DNS server, wherein the DNS query is associated with a requested resource; dynamically determining, at the first DNS server, a routing mode from a plurality of available routing modes for providing the requested resource; and transmitting, to the client computing device, a response to the DNS query in accordance with the determined routing mode.
 6. The computer-implemented method of claim 5, wherein the plurality of available routing modes includes two or more of a default routing mode, a sloppy routing mode, a regional anycast routing mode, or an anycast routing mode.
 7. The computer-implemented of claim 5, wherein the routing mode is dynamically determined based on one or more criterion.
 8. The computer-implemented method of claim 7, wherein the one or more criterion comprises at least one of a susceptibility factor associated with an individual one of the plurality of available routing modes or a latency for providing the requested resource associated with individual one of the plurality of available routing modes.
 9. The computer-implemented method of claim 5, wherein the determined routing mode is a sloppy routing mode.
 10. The computer-implemented method of claim 5 further comprising: selecting, at the first DNS server, (a) an alternative resource identifier associated with a second DNS server at a second POP of the CDN service provider or (b) an IP address of a cache component at the second POP of the CDN service provider, wherein the alternative resource identifier includes information for causing a second DNS query to resolve to the second DNS server of the CDN service provider.
 11. The computer-implemented method of claim 10, wherein the response is the alternative resource identifier.
 12. The computer-implemented method of claim 11 further comprising: obtaining the second DNS query from the client computing device at the second DNS server, wherein the second DNS query is associated with the alternative resource identifier provided by the CDN service provider; selecting, at the second DNS server, a cache component for providing the requested resource; and transmitting, to the client computing device, information identifying the selected cache component.
 13. A system comprising: a first point of presence (POP) associated with a content delivery network (CDN) service provider, wherein the first POP includes a first domain name system (DNS) server that receives a first DNS query from a client computing device and a cache server in communication with the first DNS server, wherein the first DNS query is associated with a requested resource, and wherein the first DNS server is operative to: select a routing mode from a plurality of available routing modes for providing the requested resource; dynamically select (a) an alternative resource identifier associated with a second DNS server at a second POP of the CDN service provider or (b) an IP address of a cache component of the CDN service provider, wherein the alternative resource identifier includes information for causing a second DNS query to resolve to the second DNS server of the CDN service provider; and transmit, to the client computing device, the alternative resource identifier or the IP address in accordance with the selected routing mode.
 14. The system of claim 13, wherein the selection of the alternative resource identifier or the IP address is based at least in part on the determined routing mode.
 15. The system of claim 13, wherein the selected routing mode is a sloppy routing mode.
 16. The system of claim 13, wherein the routing mode is dynamically selected based on one or more criterion.
 17. The system of claim 16, wherein the one or more criterion comprises at least one of a susceptibility factor associated with the first POP, a susceptibility factor associated with the second POP, or a latency associated with the second POP for providing the requested resource.
 18. The system of claim 17, wherein the selected routing mode is a regional anycast routing mode and wherein the regional anycast routing mode is selected based at least in part on the susceptibility factor of the first POP and the susceptibility factor of the second POP.
 19. The system of claim 13, wherein the one or more criterion comprises at least one of a network usage associated with an original content provider and a content delivery bandwidth associated with the CDN service provider, wherein the network usage is based at least in part on content provider pricing information and wherein the content delivery bandwidth is based at least in part on CDN service provider cost information.
 20. The system of claim 13, wherein the selected routing mode is a default routing mode, wherein the default routing mode is a latency-based routing mode that reduces a latency for providing the requested resource. 